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Charging method, charging equipment, and integrated circuit |
| 6124700 |
Charging method, charging equipment, and integrated circuit
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| Patent Drawings: | |
| Inventor: |
Nagai, et al. |
| Date Issued: |
September 26, 2000 |
| Application: |
08/809,724 |
| Filed: |
August 10, 1998 |
| Inventors: |
Nagai; Tamiji (Kanagawa, JP)
Ozawa; Kazunori (Kanagawa, JP)
Suzuki; Kuniharu (Tokyo, JP)
Yamazaki; Kazuo (Kanagawa, JP)
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| Assignee: |
Sony Corporation (Tokyo, JP) |
| Primary Examiner: |
Wong; Peter S. |
| Assistant Examiner: |
Luk; Lawrence |
| Attorney Or Agent: |
Maioli; Jay H. |
| U.S. Class: |
320/130; 320/132 |
| Field Of Search: |
320/132; 320/130; 320/152; 320/153; 320/157; 320/159; 320/162 |
| International Class: |
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| U.S Patent Documents: |
5355073; 5391974; 5408170; 5465039; 5637981; 5977749 |
| Foreign Patent Documents: |
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| Other References: |
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| Abstract: |
When a secondary battery such as a lithium ion battery, etc. requiring constant-voltage charging is charged, the battery voltage and charging current of the secondary battery are detected under a specified state, and in accord with the detected state, a voltage at which charging is carried out, the charging time or charging stop period thereof, or connecting condition of the charging circuit etc. are controlled in order to favorably charge the secondary battery to a full-charge or to a nearly full-charged state, thereby effectively preventing deterioration of characteristics of the secondary battery. |
| Claim: |
What is claimed is:
1. A charging method for a secondary battery, comprising:
detecting a charging current;
changing over a voltage applied to said secondary battery to a second voltage lower than a first voltage when said charging current reaches a first charging current corresponding to a substantially charged condition of said secondary batteryduring charging while said first voltage is applied to said secondary battery; and
changing over said voltage applied to said secondary battery to said first voltage when said charging current exceeds a second charging current corresponding to a discharging battery voltage while said second voltage is applied to said secondarybattery.
2. The charging method according to claim 1, wherein said second charging current is equal to said first charging current.
3. The charging method according to claim 1, further comprising:
measuring one of an internal temperature and an environmental temperature surrounding said secondary battery; and
changing over the application of said second voltage to the application of a third voltage instead of said first voltage when said measured temperature exceeds a specified temperature, wherein said third voltage is in a range between said firstand second voltages.
4. The charging method according to claim 3, wherein said third voltage is continuously changed in response to said measured temperature.
5. A charging method for a secondary battery, comprising:
detecting a charging current;
changing over a voltage applied to said secondary battery to a second voltage lower than a first voltage when a voltage of said secondary battery corresponding to a substantially charged condition is detected during charging said secondarybattery while applying said first voltage; and
changing over said voltage applied to said secondary battery to said first voltage when said charging current reaches a specified charging current while said second voltage is applied to said secondary battery.
6. The charging method according to claim 5, further comprising changing over the application of said second voltage to the application of a third voltage in a range between said first and second voltages instead of said first voltage when oneof an internal temperature and an environmental temperature surrounding said secondary battery reaches a specified temperature or higher.
7. The charging method according to claim 6, wherein said third voltage is continuously changed in response to said detected temperature.
8. A charging method for a secondary battery, comprising:
detecting a potential across respective ends of a switching means for controlling a supply of a charging power supply to said secondary battery and a potential across respective ends of said secondary battery while a low-voltage charging powersupply is fed to said secondary battery; and
turning on said switching means based on said detected potentials for starting charging of said secondary battery with said supply of said charging power supply being fed to said secondary battery at a specified voltage.
9. The charging method according to claim 8, wherein a field effect transistor is used as said switching means to increase an impedance across respective ends of said field effect transistor and for detecting said potential.
10. The charging method according to claim 8, wherein a voltage of said charging power supply when detecting said potential is set to a value of about the lowest required voltage for controlling said switching means.
11. The charging method according to the claim 8, wherein said supply of said charging power supply is increased in response to with an increase of said potential across said respective ends of said secondary battery after the start of saidcharging.
12. The charging method according to claim 8, wherein said supply of said charging power supply is changed in a plurality of stages and increased in response to an increase of said potential across said respective ends of said secondary batteryafter said charging begins.
13. The charging method according to claim 8, wherein said supply of said charging power supply when said potential is detected is lowered to a voltage below the minimum required for controlling said switching means, and
said charging power supply is accumulated in a charge-storage means, thereby securing a charge required for carrying out a corresponding control by said switching means.
14. The charging method according to claim 8, wherein after charging is stopped when a substantially fully charged state of said secondary battery is detected and when said secondary battery is detected to be at a specified electrical state,
charging of said secondary battery is restarted after a specified time passes from this detection.
15. The charging method according to claim 14, wherein said specified electrical state is detected by detecting that a battery voltage of said secondary battery is lower by a specified value than a standard voltage with which said chargingvoltage is set.
16. The charging method according to claim 14, wherein said specified electrical state is detected by detecting that a battery voltage reaches a specified voltage from a voltage value with a grounding potential of said secondary battery set as astandard.
17. The charging method according to claim 14, wherein said specified electrical state is detected by detecting that a charging current reaches a specified value when a predetermined voltage is applied to said secondary battery.
18. The charging method according to claim 17, wherein said predetermined voltage is a voltage lower than said supply of said charging power supply.
19. The charging method according to claim 8, further comprising:
detecting an electrical condition of said secondary battery periodically when a specified time passes from a time when a substantially fully charged state of said secondary battery is detected and charging is stopped; and
restarting said charging when said detected electrical condition is a specified condition.
20. The charging method according to claim 19, wherein charging is restarted after said specified time passes from a time when said specified electrical condition is detected.
21. The charging method according to claim 19, wherein said specified condition is a charging current exceeding a specified value when a charging voltage or a voltage lower than said charging voltage is applied to said secondary battery.
22. The charging method according to claim 19, wherein said specified condition is detected when a voltage of said secondary battery equals said specified voltage.
23. The charging method according to claim 22, wherein when said voltage of said secondary battery does not reach said specified voltage and charging is not restarted, an energy required for detecting said voltage is charged in said secondarybattery.
24. The charging method according to claim 22, wherein said specified condition is detected when a battery voltage is lower than a specified voltage.
25. The charging method according to claim 22, wherein said specified condition is detected when a battery voltage equals said specified voltage value from a voltage set with a grounding potential of said secondary battery designated as astandard.
26. A charging equipment for a secondary battery, comprising:
first voltage feeding means for feeding a first voltage to said secondary battery;
second voltage feeding means for feeding a second voltage lower than said first voltage to said secondary battery;
current detection means for detecting a charging current to said secondary battery; and
control means for changing over said first voltage feeding means to said second voltage feeding means based on an output of said current detection means, wherein when said current detecting means detects a first charging current corresponding toa substantially charged condition of said secondary battery said first voltage feeding means is changed over to said second voltage feeding means, and when said current detection means detects a current exceeding a second charging current while saidsecond voltage feeding means is applied, said second voltage feeding means is changed over to said first voltage feeding means.
27. The charging equipment according to claim 26, wherein said first charging current is equal to said second charging current.
28. The charging equipment according to claim 26, further comprising:
third voltage feeding means for feeding a third voltage in a range between said first and second voltages to said secondary battery; and
temperature detection means for detecting one of an internal temperature and an environmental temperature surrounding said secondary battery, wherein when said detected temperature exceeds a specified temperature said second voltage feeding meansis changed over to said third voltage feeding means instead of said first voltage feeding means.
29. The charging equipment according to claim 28, wherein an output voltage of said third voltage feeding means is continuously changed in response to
said detected temperature.
30. A charging equipment for a secondary battery, comprising;
first voltage feeding means for feeding a first voltage to said secondary battery;
second voltage feeding means for feeding a second voltage lower than said first voltage to said secondary battery;
current detection means for detecting a charging current to said secondary battery;
voltage detection means for detecting a secondary battery voltage; and
control means for changing over said first voltage feeding means to said second voltage feeding means based on outputs of said voltage and current detection means, wherein when a specified voltage corresponding to a substantially chargedcondition of said secondary battery is detected by the voltage detection means said first voltage feeding means is changed over to said second voltage feeding means, and when said current detection means detects a current exceeding a specified chargingcurrent while said second voltage feeding means is applied to said secondary battery said second voltage feeding means is changed over to said first voltage feeding means.
31. The charging equipment according to claim 30, further comprising;
third voltage feeding means for feeding a third voltage in a range between said first and second voltages to said secondary battery; and
temperature detection means for detecting one of an internal temperature and an environmental temperature surrounding said secondary battery, wherein when said detected temperature of said temperature detecting means exceeds a specifiedtemperature said second voltage feeding means is changed over to said third voltage feeding means instead of said first voltage feeding means.
32. The charging equipment according to claim 31, wherein said third output voltage of said third voltage feeding means is continuously changed in response to said temperature detected by said temperature detecting means.
33. A charging equipment for a secondary battery, comprising:
a power supply circuit for feeding a charging power to said secondary battery;
switching means for controlling said power supply circuit feed to said secondary battery;
detecting means for detecting a potential across respective ends of said switching means and a potential across respective ends of said secondary battery while a low-voltage charging power is fed from said power supply circuit to said secondarybattery; and
charging control means for starting charging of said secondary battery by turning on said switching means in response to said detected potentials by said detection means and for controlling said power supply circuit to feed a specified voltage tosaid secondary battery.
34. The charging equipment according to claim 33, wherein a field-effect transistor is used as said switching means, and said potential is detected by the said detection means by increasing an impedance across respective ends of saidfield-effect transistor.
35. The charging equipment according to claim 33, wherein a voltage of said power supply circuit when detected by said detection means is set to a value of about the lowest voltage required for controlling said switching means.
36. The charging equipment according to claim 33, wherein said charging power of said power supply is increased in response to an increase of said potential across said respective ends of said secondary battery after starting said charging.
37. The charging equipment according to claim 33, wherein said charging power of said power supply circuit is varied in a plurality of stages in response to an increase of said potential across said respective ends of said secondary batteryafter starting said charging.
38. The charging equipment according to claim 33, wherein a charged load storage means is connected across said power supply circuit and said charging control means; and
said charging power of said power supply circuit detected by said detection means is lowered to the minimum power required for controlling said switching means.
39. The charging equipment according to claim 33, further comprising:
battery condition detecting means for detecting a condition of said secondary battery; and
a timer triggered by said battery condition detecting means, wherein when a specified time passes from a start of operation of said timer means said charging control means starts charging said secondary battery.
40. The charging equipment according to claim 39, wherein said condition of said secondary battery is a specified voltage.
41. The charging equipment according to claim 39, wherein said condition of said secondary battery is a charging current of a specified value when a predetermined voltage is applied to said secondary battery.
42. The charging equipment according to claim 41, wherein said predetermined voltage for pre-charging is a voltage lower than said charging voltage.
43. The charging equipment according to claim 39,
wherein said timer means is triggered when said battery condition detection means detects a substantially fully charged condition of said secondary battery, and said charging control means controls said battery condition detection means to detecta condition of said secondary battery periodically when a specified time passes from a time when said timer is triggered, and when said detected condition is a specified condition charging is restarted.
44. The charging equipment according to claim 43, wherein charging is restarted when said specified time passes from a time when said specified condition is detected.
45. The charging equipment according to claim 43, wherein said battery condition detection means detects a charging current exceeding a specified value when a charging voltage or a voltage lower than said charging voltage is applied to the saidsecondary battery.
46. The charging equipment according to claim 43, wherein said battery condition detection means detects a battery voltage of said secondary battery equal to said specified voltage.
47. The charging equipment according to claim 46, wherein an energy required for detecting a battery voltage is charged in said secondary battery by controlling said charging control means when said secondary battery voltage does not reach saidspecified voltage and charging is not restarted.
48. An integrated circuit for controlling charging of a secondary battery, in which a charging current to said secondary battery is detected and control is carried out for selectively supplying a first voltage and a second voltage lower thansaid first voltage to said secondary battery, wherein
when said secondary battery is judged to be at a substantially charged condition based on a first value of said detected charging current while said first voltage is applied to said secondary battery said first voltage is changed over to saidsecond voltage, and
when said secondary battery is judged to be in a discharging condition based on a second value of said detected charging current while said second voltage is applied to said secondary battery, said second voltage is changed over to said firstvoltage.
49. The integrated circuit according to claim 48, wherein one of an internal temperature and an environmental temperature surrounding said secondary battery is measured, and when said measured temperature exceeds a specified temperature controlis carried out for applying a third voltage in a range between said first voltage and said second voltage to said secondary battery.
50. The integrated circuit according to claim 48, wherein said third voltage is controlled to be continuously changed in response to said measured temperature.
51. An integrated circuit for controlling charging of a secondary battery, in which a charging current to said secondary battery is detected and control is carried out for selectively supplying a first voltage and a second voltage lower thansaid first voltage to said secondary battery, wherein
when said secondary batter is judged to be at a substantially charged condition based on a value of a detected charging voltage while said first voltage is applied to said secondary battery said first voltage is changed over to said secondvoltage, and
when said secondary battery is judged to be in a discharging condition based on a value of said detected charging current while said second voltage is applied to said secondary battery, said second voltage is changed over to said first voltage.
52. The integrated circuit according to claim 51, wherein one of an internal temperature and an environmental temperature surrounding said secondary battery is measured, and when said measured temperature exceeds a specified temperature controlis carried out for applying a third voltage in a range between said first voltage and said second voltage to said secondary battery.
53. The integrated circuit according to claim 52, wherein said third voltage is controlled to be continuously changed in response to said measured temperature.
54. An integrated circuit for controlling charging of a secondary battery, wherein
a potential across respective ends of a switching means for controlling a supply of a charging power supply to said secondary battery and a potential across respective ends of said secondary battery is detected while a low-voltage charging powersupply is fed to said secondary battery, and
said switching means is controlled based on said detected potentials for starting charging of said secondary battery with said supply of said charging power supply supplied being fed to said secondary battery at a specified voltage.
55. The integrated circuit according to claim 54, wherein said detected potential across respective ends of said secondary battery is judged after said charging begins, and
controls is carried out to raise said supply of said charging power supply in response to an increase of said judged potential.
56. The integrated circuit according to claim 54, wherein a detected value of said potential across said respective ends of said secondary battery is judged after said charging begins, and
control is carried out for raising said supply of said charging power supply by varying said supply in a plurality of stages in response to an increase of said judged potential.
57. The integrated circuit according to claim 54, wherein
when it is judged that the battery is at a specified electrical condition and after charging is stopped when a substantially fully charged state of said secondary battery
is detected, charging of said secondary battery is restarted after a specified time passes from the judgment of said specified electrical condition.
58. The integrated circuit according to claim 57, wherein said specified electrical condition is judged by judging that a battery voltage of said secondary battery reaches a specified voltage.
59. The integrated circuit according to claim 57, wherein said specified electrical condition is judged by judging that a charging current reaches a specified current value when a specified voltage is applied to said secondary battery.
60. The integrated circuit according to claim 59, wherein said specified voltage is lower than said supply of said charging power supply.
61. The integrated circuit according to claim 54, wherein
a specified electrical condition of said secondary battery is judged periodically when a specified time passes from a time when a substantially fully charged state of said secondary battery is detected and charging is stopped, and
when it is judged that said battery enters said specified electrical condition said charging is restarted.
62. The integrated circuit to claim 61, wherein charging is restarted after said specified time passes from a time when it is judged that said specified electrical condition is reached.
63. The integrated circuit according to claim 61, wherein said specified electrical condition is a detected charging current exceeding a specified value when a charging voltage or a voltage lower than said charging voltage is applied to saidsecondary battery.
64. The integrated circuit according to claim 61, wherein said specified electrical condition is a detected secondary battery voltage equal to said specified voltage.
65. The integrated circuit according to claim 64, wherein control is carried out so that at least an energy required for detecting a battery voltage is charged in said secondary battery when said detected secondary battery voltage does not reachsaid specified voltage and charging is not restarted. |
| Description: |
TECHNICAL FIELD
The present invention relates to a charging method and charging equipment for secondary batteries and an integrated circuit used for its charging control, and more particularly to a charging method and charging equipment suitable for applying tosecondary batteries which require constant-voltage charging such as lithium ion batteries or the like and an integrated circuit used for its charging control.
BACKGROUND ART
Conventionally, for secondary batteries which are able to be charged and require constant-voltage charging, lithium ion batteries are developed. This lithium ion battery is charged with the characteristics shown, for example, in FIG. 1. FIG. 1is a characteristic diagram of charging current/voltage vs. elapsed time of a general lithium ion battery, in which charging is carried out with a charging current I set as a constant current from the initiation of charging until the battery voltagereaches a specified potential. Carrying out this constant-current charging increases a battery voltage V and when it exceeds a specified value, charging is changed over to constant-voltage charging. In this event, for example, voltage V.sub.1corresponding to battery voltage when the lithium ion battery is fully charged (that is, 100% charged) is supplied. Carrying out this constant-voltage charging charges the lithium ion battery, causes the battery voltage to rise to voltage V.sub.1, butas this charging takes place, the charging current I decreases. Now, when this charging current I decreases to a specified value, it is judged that the lithium ion battery is 100% charged (or charged nearly to 100%), and supply of charging current isstopped.
Charging in this way allows the lithium ion battery to be efficiently charged to 100%.
Now, the lithium ion battery charged to 100% in this way may sometimes have the characteristics deteriorated by the charging condition thereafter. That is, if the voltage V.sub.1 corresponding to battery voltage when the lithium ion battery isfully charged is constantly applied to the 100% charged lithium ion battery from the charging equipment as charging voltage and small-power charging is repeatedly carried out, the charging condition can be maintained to nearly 100% condition even whenthere is self-discharge. However, when such nearly 100% condition continues, the lithium ion battery becomes characteristics which tends to gradually reduce the chargeable capacity, and eventually deteriorates the characteristics as a secondary battery.
In order to prevent characteristics deterioration due to the continuation of the 100% charged condition, for example, stopping charging at about 90% of the charging capacity is assumed, but this results in inconvenience that the capacity preparedas a secondary battery is not effectively utilized.
When temperature of the battery itself rises, the lithium ion battery has a disadvantage that the chargeable capacity decreases and battery characteristics rapidly deteriorate, and it also has a disadvantage that it is not preferable to becharged to the full charging level with the battery temperature increased at the time of charging under the same conditions as those free of temperature rise.
As described above, it is when there remains scarcely charged voltage in the lithium ion battery to carry out constant-current charging at first and then change over to constant-voltage charging to charge the battery, and when any voltage remainsin the battery, it is necessary to carry out constant-voltage charging with the charging current reduced, thereby preventing deterioration of characteristics as a secondary battery resulting from rapid charging by large current.
Consequently, before charging is started, the condition of the battery to be charged must be detected and the remaining voltage must be detected. In order to detect this remaining voltage, charging is carried out with a small current calledpre-charging at the start of charging, the battery voltage, etc. at that time is detected, and the remaining voltage of the battery is detected.
FIG. 2 shows one example of a circuit configuration of a conventional charging equipment which can carry out the pre-charging, in which to one end on the secondary side (primary side is omitted) of a switching transformer 1 that composes theswitching power supply, the anode of diode 2 is connected, and the cathode of this diode 2 and the other end on the secondary side of a transformer 1 are connected with a capacitor 3, and direct current power supply of a specified voltage is obtained byrectification by diode 2 and smoothing by capacitor 3.
The cathode of diode 2 is connected to one end (positive electrode) of a secondary battery (lithium ion battery) 4 loaded to this charging equipment via an opening and closing switch SW1, and the other end (negative electrode) of this secondarybattery 4 is connected to the other end on the secondary side of the switching transformer 1. In parallel to the opening and closing switch SW1, a series circuit comprising an opening and closing switch SW2 and a resistor 5 is connected.
In this event, opening and closing of switches SW1 and SW2 are controlled by a control circuit 6. This control circuit 6 is connected in such a manner that the power supply is fed from the secondary side of the
switching transformer 1 and is operated by this power supply. And this control circuit is designed to detect the condition of the secondary battery 4 by some method not illustrated (for example, detection of battery voltage).
To explain the control by the control circuit 6, at the start of charging, the switch SW2 is held closed, while the switch SW1 is held open. Keeping the switches in this condition allows the power supply to be fed from the secondary side ofswitching transformer 1 with the resistor 5 connected to the secondary battery 4 in series, reduces the charging current to be fed to the secondary battery 4 as much as the loss caused by this resistor 5, and allows pre-charging by small current to takeplace. And under this pre-charging condition, the battery condition such as battery voltage of the secondary battery 4 or the like is detected by the control circuit 6, and if the detected condition is judged to be the condition with little remainingvoltage that allows rapid charging, switch SW1 is held closed, switch SW2 is held open, charging current is supplied to the secondary battery 4 with the resistor 5 in the condition free of loss, and rapid charging by large current is begun.
Now, FIG. 3 shows the charging characteristics when switch SW1 is turned on and those when switch SW2 is turned on, indicating that comparatively large current is allowed to flow at a given voltage as charging characteristics when switch SW1 isturned on. The charging characteristics when switch SW2 is turned on are such that the current value is suppressed to a small value.
In this way, configuring to provide a plurality of paths for accommodating the charging current and to vary the charging current to carry out pre-charging results in complicated configuration of the charging equipment as much and constitutes aninconvenience.
As a configuration of another charging equipment for enabling conventional pre-charging, there is one with the circuit configuration shown in FIG. 4. In the case of this circuit, the cathode of diode 2 is connected to one end (positiveelectrode) of the secondary battery 4 (lithium ion battery) mounted to this charging equipment via an opening/closing closing switch SW3, and the other end (negative electrode) of this secondary battery 4 is connected to the other end on the secondaryside of the switching transformer 1.
And opening and closing of the switch SW3 are controlled by a control circuit 7. This control circuit 7 is connected in such a manner that the power supply is fed from the secondary side of the switching transformer 1. And this control circuitis designed to detect the condition of the secondary battery 4 by some method not illustrated (for example, detection of battery voltage), and opening and closing of switch SW3 are controlled based on the detected condition.
Now, to explain the control condition of switch SW3, in carrying out ordinary charging (rapid charging, etc.), switch SW3 is continuously held closed, and in carrying out pre-charging with small current, opening and closing of switch SW3 arerepeatedly carried out. That is, for example, as shown in FIG. 5, when precharging is carried out at the start of charging, ON/OFF of switch SW3 are repeated to intermittently supply a specified current value I to the secondary battery 4, and averagecharging current is lowered, bringing about the conditions in which pre-charging Pre is able to be carried out by small current. When precharging is switched to ordinary charging, switch SW3 is continuously held closed, and charging by the specifiedcurrent value I is continuously carried out.
Pre-charging by intermittently opening and closing this switch in this way enables both ordinary charging and pre-charging only by installing one switch, but at the time of pre-charging by ON/OFF of this switch, the peak current when opening andclosing of the switch are changed over is transmitted to the control circuit 7, and there is a high possibility to adversely affect operation of the control circuit 7. Consequently, pre-charging by repeating ON/OFF of the switch in this way is notpreferable.
Another problem is an error in detection of battery voltage in the battery charger, and there is a case in which the error deteriorates the battery characteristics.
That is, FIG. 6 shows one example of the charging control condition when the conventional lithium ion battery is 100% charged. For example, suppose that a lithium ion battery with voltage V.sub.1 when fully charged is charged and the batteryvoltage of this battery reaches V.sub.1 at a certain timing t.sub.1. In this event, this lithium ion battery is judged to be fully charged and supply of charging current is stopped. Stopping charging causes the lithium ion battery to gradually reducebattery voltage due to self discharge or discharge to the load circuit.
Now, the charging circuit is set to restart charging when the battery voltage reaches a predetermined voltage V.sub.2. Suppose that the charging circuit detects this battery voltage V.sub.2 at timing t.sub.2, then, charging is restarted at thistiming t.sub.2, and the battery voltage rises again as shown with characteristic Vx, achieving the fully charged condition.
By setting in this way, the battery voltage is able to be held to the voltage close to full charging. Now the lithium ion battery is constantly charged nearly 100% by bringing the voltage V.sub.2 to restart charging to a voltage value extremelyclose to the battery voltage V.sub.1 when fully charged, but since achieving this state accelerates deterioration of the battery, voltage V.sub.2 to restart charging shall be set to the voltage slightly reduced from the battery voltage V.sub.1 when fullycharged to allow the remaining battery voltage to vary in a certain range, thereby preventing deterioration of the battery.
However, in general, in the voltage detection circuit with comparatively simple configuration built into this kind of battery charger, it is difficult to constantly accurately detect voltage V.sub.12, and an error .DELTA.V is generated in thedetection value of the voltage. Now, as shown in FIG. 6, if a voltage higher than actual setting by the error .DELTA.V is judged to be the voltage V.sub.1 (timing t.sub.2 '), the battery returns to the fully charged condition more quickly than theoriginally set condition (condition by characteristic Vx) as in the case of the characteristic Vy shown with broken line, and deterioration of the battery characteristics is accelerated.
In addition, when the secondary battery is charged to full charge and charging is stopped, depending on the condition on the battery charger side, there is a case in which discharge current is generated from the secondary battery to the batterycharger side, and in such event, charging of the secondary battery is restarted in a short time, shortening the frequency to carry out charging.
DISCLOSURE OF THE INVENTION
In view of the foregoing problems, it is the first object of the invention to effectively utilize the battery capacity without deteriorating the battery.
The second object is to detect the battery condition in a simple construction and accurately upon charging.
The third object is to effectively charge the battery without deteriorating the battery even if there is any detection error in the battery condition.
The fourth object is to prevent wasteful discharge from the secondary battery in the fully charged condition of the secondary battery.
The first invention is a charging method to change over the voltage applied to the secondary battery to the second voltage lower than the first voltage when charging current is detected during charging by applying the first voltage to thesecondary battery and the first charging current corresponding to the nearly fully charged condition of the said secondary battery is detected in the charging method for charging the secondary battery which is charged by constant-voltage charging, aswell as to change over the voltage application to that of the first voltage when the current exceeding the second charging current corresponding to the specified remaining battery voltage is detected, with the second voltage applied to the secondarybattery. By this charging method, only when the remaining battery voltage lowers to the specified value, the battery is charged to the fully charged condition by the first voltage. Consequently, after the battery is once charged to the fully chargedcondition, charging to full charge is repeated every time the battery lowers to the specified remaining battery voltage, and the secondary battery condition can be constantly maintained to the nearly fully charged condition, and at the same time, becausethe second voltage lower than the first voltage is applied to the battery except when charging to this full charge is carried out, the secondary battery is not continuously brought to the fully charged condition, and deterioration in secondary batteryperformance caused by continued fully charged condition can be prevented.
The second invention uses the same current value for the said second charging current and the said first charging current in the charging method according to the first invention. According to this charging method, charging condition can besuccessfully controlled.
The third invention is a charging method according to the first invention designed to detect temperature inside or in the vicinity of the said secondary battery, and to change over the application of the said second voltage to the application ofthe third voltage of the potential across the said first and the second voltages in place of changing it over to the said first voltage when the detected temperature exceeds a specified temperature. According to this charging method, it is possible tosuppress deterioration of secondary battery performance caused by temperature rise.
The fourth invention is a charging method according to the third invention designed to continuously change the said third voltage in accordance with the temperature detected as above. According to this charging method, charging controlcorresponding to temperature is favorably carried out.
The fifth invention is a charging method to detect the battery voltage of the said secondary battery while charging the said secondary battery by applying the first voltage according to the charging method of the secondary battery where chargingtakes place by constant-voltage charging, to change over the voltage applied to the said secondary battery to the second voltage lower than the said first voltage when a specified voltage corresponding to the nearly full-charge state of the saidsecondary battery is detected, and at the same time, to change over to application of the said first voltage when a specified charging current is detected with this second voltage applied to the secondary battery. According to this charging method, thebattery is charged to nearly full-charge state only when the remaining battery voltage lowers to a specified value. Consequently, once after it is charged to the full-charge state, charging to the full-charge is repeatedly carried out every time thebattery remaining voltage lowers to a specified value, thereby maintaining the secondary battery condition constantly to nearly full-charge state, and at the same time, because except when this charging to the full-charge is carried out, the secondaryvoltage lower than the first voltage is applied, the secondary battery is not continuously brought to the full-charge state and thereby deterioration of the secondary battery performance caused by continuation of the full-charge state can be prevented.
The sixth invention is a charging method according to the fifth invention wherein the application of the said second voltage is changed over to the application of the third voltage of the potential between the said first and the second voltagesin place of changing it over to application of the said first voltage when temperature inside or in the vicinity of the said secondary battery is detected and the detected temperature is a specified temperature or higher. According to this chargingmethod, it is possible to favorably control the charging state.
The seventh invention is a charging method according to the sixth invention designed to continuously change the said third voltage in accord with the temperature detected as above. According to this charging method, it is possible to favorablycontrol charging in accord with the temperature.
The eighth invention is a charging method designed to detect the potential across one end and the other end of a switching means for controlling start and stop of supply of the charging power supply to the said secondary battery or the potentialacross one end and the other end of the said secondary battery with low-voltage charging power supply fed to the said secondary battery in the charging method for charging the secondary battery which requires constant-current charging at the start ofcharging, to turn on the said switching means based on this detected potential, and at the same time to start charging to the secondary battery with the charging power supply to be fed to the said secondary battery designated as a specified potential. According to this charging method, it is possible to control the switching means and to detect the secondary battery condition based on the detection of the potential across one end and the other end of this switching means or the potential across oneend and the other end of the secondary battery, thereby enabling accurate detection of the secondary battery condition as in the case of the conventional pre-charging. Consequently, it is possible to accurately detect the secondary battery conditionwithout providing a charging circuit specialized for pre-charging and to simplify the circuit configuration of the charging equipment.
The ninth invention is a charging method according to the eighth invention designed to use a field effect transistor as the said switching means, to increase the impedance across one end and the other end of this field effect transistor, and todetect the said potential. According to this charging method, only carrying out the impedance control of the field effect transistor, it is possible to easily detect the secondary battery condition, and at the same time to reduce the loss of the fieldeffect transistor even when the battery voltage of the secondary battery is low or shorted.
The tenth invention is a charging method according to the eighth invention designed to keep the potential of the said charging power supply when the said potential is detected to the value in the vicinity of the lowest required voltage forcontrolling the said switching means. According to this charging method, it is possible to detect the secondary battery condition with the lowest voltage charging power supply fed to the secondary battery, and to detect the electrical condition of thesecondary battery with the minimum load applied to the secondary battery and the circuit, as well as to detect the secondary battery electrical state under the favorable condition.
The 11th invention is a charging method according to the eighth invention designed to raise the potential of the said charging power supply in accord with an increase of the potential across one end and the other end of the said secondary batteryafter the start of the said charging. According to this charging method, it is possible to nearly uniformly hold the electric power applied to the switching means, and it is also possible to hold the switching means to a favorable condition.
The 12th invention is a charging method according to the eighth invention designed to change and increase the potential of the said charging power supply in a plurality of stages in accord with an increase of the potential across one end and theother end of the secondary battery after the said charging begins. According to this charging method, it is possible to nearly uniformly keep the electric power applied to the switching means, and it is also possible to keep the switching means to thefavorable condition. In this case, since voltage is allowed to be varied in a plurality of stages, a simple control is only required for the voltage circuit.
The 13th invention is a charging method according to the eighth invention designed to lower the potential of the said charging power supply, when the said potential is detected, to the voltage below the minimum required one for controlling thesaid switching means, and at the same time to accumulate this charging power supply by a charge-storage means, thereby securing the potential required for carrying out the corresponding control by the said switching means. According to this chargingmethod, as long as electric charge is accumulated in the charge-storage means, it is possible to keep the voltage of the charging power supply to be fed to the
secondary battery when the voltage is detected with a detection means to the voltage lower than the one which can control the switching means, enabling the detection of the secondary battery condition more favorably with lower voltage applied.
The 14th invention is a charging method for enabling the restart of charging of the secondary battery after a specified time passes from this detection when the said secondary battery is detected to achieve a specified electrical state aftercharging is stopped when the nearly full-charge state is detected in a charging method for charging the secondary battery which is carried out by constant-voltage charging. According to this charging method, it is possible to designate the time torestart charging once it comes in the full-charge state (or nearly full-charge state) to the time in which a specified time is added to the time for a battery to reach a specified electrical condition, and even if any error exists in the detected batterycondition, it is possible to secure a certain time for returning to the full-charge condition, and it is thereby possible to prevent deterioration of characteristics of the secondary battery caused by continuation of the full-charge conditions.
The 15th invention is a charging method according to the 14th invention designed to detect the said specified electrical condition and to detect that the battery voltage of the said secondary battery lowers by a specified value from the voltagewith the said charging voltage set as a standard. According to this charging method, it is possible to exactly detect the decrease of battery voltage with the charging voltage as a standard, and to accurately control the condition of the secondarybattery.
The 16th invention is a charging method according to the 14th invention designed to detect the said specified electrical condition, and to detect that the battery voltage becomes a specified voltage from the voltage value with the groundingpotential of the said secondary battery set as a standard. According to this charging method, it is possible to properly control the secondary battery condition by comparatively simple voltage detection.
The 17th invention is a charging method according to the 14th invention designed to detect that the charging current when a specified voltage is applied to the said secondary battery becomes a specified value as detection of the said requiredelectrical condition. According to this charging method, it is possible to properly control the charging condition of the secondary battery based on the detection of the current value.
The 18th invention is a charging method according to the 17th invention wherein the said required voltage is lower than the charging voltage of the said constant voltage. According to this invention, it is possible to detect the secondarybattery condition by the voltage lower than the charging voltage, and to properly detect the battery condition with a load applied to the secondary battery reduced.
The 19th invention is a charging method for charging the secondary battery with the constant voltage charging voltage, which is designed to detect the electrical condition of the said secondary battery every time a specified time passes from thetime when the nearly full-charge of the secondary battery is detected to the time when charging is stopped, and to restart charging when this detected electrical condition is a specified condition. According to this charging method, it is possible tokeep the time open at least for the specified period from the time when charging is stopped once full-charge condition is attained to the time when charging is restarted, thereby enabling preventing of deterioration of the secondary batterycharacteristics.
The 20th invention is a charging method according to the 19th invention designed to restart charging after a specified time passes from the time when the specified electrical condition is detected. According to this charging method, it ispossible to more effectively secure the time before it returns to the full-charge condition and to more improve the effect to prevent deterioration of the secondary battery characteristics.
The 21st invention is a charging method according to the 19th invention designed to detect that the charging current exceeds a specified value when the said charging voltage or voltage lower than this charging voltage is applied to the saidsecondary battery for the detection of the said specified electrical condition. According to this charging method, it is possible to accurately detect the secondary battery condition from the charging current.
The 22nd invention is a charging method according to the 19th invention designed to detect that the battery voltage of the said secondary battery attains the specified voltage for the detection of the said specified electrical condition. According to this charging method, it is possible to accurately detect the secondary battery condition from the battery voltage.
The 23rd invention is a charging method according to the 22nd invention designed to charge at least the energy required for detecting the battery voltage in the said secondary battery when the said secondary battery voltage does not attain thespecified voltage and charging is not restarted. According to this charging method, it is possible to effectively prevent the decrease of remaining voltage caused by repeating detection of the battery condition every specified time.
The 24th invention is a charging method according to the 22nd invention designed to detect that a specified voltage lowers from the voltage set by the said charging voltage designated as a standard for detection of the said specified voltage. According to this charging method, it is possible to accurately detect lowering of the battery voltage set by the charging voltage designated as a standard, and to accurately control the secondary battery condition.
The 25th invention is a charging method according to the 22nd invention designed to detect that the battery voltage attains the specified voltage value from the voltage set with the grounding potential of the said secondary battery designated asstandard for detection of the said specified voltage. According to this charging method, it is possible to accurately control the secondary battery condition by comparatively simple voltage detection.
The 26th invention is a charging method for charging the secondary battery which is designed to detect the electrical condition of the said secondary battery, to selectively supply the first and the second voltages to the said secondary batteryin accordance with the detected electrical condition, and to carry out ON/OFF control of application of the selected voltage to the said secondary battery in accord with the said detected electrical condition. According to this charging method, it ispossible to select the first and the second voltages for the voltage applied to the secondary battery, and at the same time, to be able to carry out ON/OFF control for the application of the selected voltage, and to prevent discharge from the battery tothe charging circuit side when charging voltage lower than the battery voltage is established, thereby preventing wasteful discharge of the secondary battery when voltage applied to the secondary battery is allowed to be varied.
The 27th invention is a charging method according to the 26th invention designed to charge the secondary battery with application of this voltage to the said secondary battery turned off with the said second voltage selected when the saidsecondary battery is judged to be charged to a specified value by the detection of the said electrical condition after the said first voltage is selected and applied to charge the said secondary battery when the charging voltage of the said secondarybattery is lower than the specified value by the detection of the said electrical condition, and it is also designed to charge the secondary battery with the application of the said second voltage to the said secondary battery turned on when thesecondary battery voltage is judged to be lower than the said second voltage. According to this charging method, it is possible to effectively prevent wasteful discharge from the secondary battery and at the same time to be able to charge the secondvoltage to the secondary battery free of detrimental effects when charging is restarted.
The 28th invention is a charging method according to the 27th invention designed to judge that the said secondary battery voltage is lower than the said second voltage when it is judged that the voltage is lower than the said second voltage againin a specified time after it is judged at least once that the voltage is lower than the said second voltage. According to this charging method, it is possible to charge the secondary battery with the second voltage when the secondary battery voltage ispositively lower than the second voltage and to restart charging under the favorable condition free of deteriorating the secondary battery.
The 29th invention is a charging method according to the 27th invention designed to apply the said second voltage to the secondary battery for charging when it is judged that the secondary battery voltage is the third voltage lower than thesecond voltage. According to this charging method, it is possible to restart charging under the favorable condition free of deteriorating the secondary battery only by judgment of the battery voltage without counting passage of time.
The 30th invention is a charging method according to the 27th invention designed to detect the potential difference between one end and the other end of a switching means for carrying out the said ON/OFF control and judge that the said secondarybattery voltage is lower than the second voltage. According to this charging method, it is possible to accurately judge the battery voltage at the restart of charging.
The 31st invention is a charging method according to the 27th invention designed to judge that the said secondary battery voltage is lower than the said second voltage when the current of the said secondary battery is judged to be lower than thespecified current value when voltage application to the said secondary battery is turned off. According to this charging method, charging process at the second voltage is carried out only when the current flowing in the load circuit is lower than thespecified value (for example, in the case of the vicinity of zero), and it is possible to prevent charging at a low voltage when the load current exceeds the specified value.
The 32nd invention is a charging method according to the 27th invention designed to detect the potential difference between one end and the other end of a switching means for carrying out the ON/OFF control when the said secondary battery currentis lower than the specified current when the application of voltage to the said secondary battery is turned off and to judge that the said secondary battery voltage is lower than the said second voltage. According to this charging method, it is possibleto judge the restart of charging by accurate voltage judgment based on the potential difference between one end and the other end of the switching means only when the current flowing in the load current is lower than the specified value.
The 33rd invention is a charging method according to the 26th invention designed to select the second voltage and charge with the application of voltage to the said secondary battery turned on when the current flowing in the secondary batteryagain at least after a specified time is judged to be lower than the said specified value after the current flowing in the secondary battery is judged to be lower than the specified value under the condition in which this second voltage is selected withthe application of voltage to the secondary battery turned off under the condition in which the second voltage is selected when the voltage is charged with the application of the voltage to the secondary battery turned on with the first voltage selectedwhen the charged voltage of the secondary battery is judged to be lower than the specified value. According to this charging method, it is possible to effectively prevent wasteful discharge from the secondary battery as well as to judge the restart ofcharging based on judgment of the current.
The 34th invention is a charging method according to the 33rd invention designed to detect the current flowing in the current path connected to the said secondary battery different from the current path fed to the said secondary battery via aswitching means for carrying out the said ON/OFF control from a means for supplying the said first and the second voltages for detection of the current flowing to the said secondary battery. According to this charging method, it is possible to detectthe stable current value not subject to fluctuation of voltage applied.
The 35th invention is a charging method according to the 26th invention designed to provide the first and the second switching means in parallel as switching means to carry out the said ON/OFF control and to supply constant current to the secondswitching means, and when the charged volume of the secondary battery is lower than the specified volume, it is designed to charge the secondary battery with the first switching means turned on and the second switching means turned off under thecondition in which the first voltage is selected when the charging volume of the secondary battery is judged to be lower than the specified volume, and when the charged volume of the secondary battery is judged to be charged to the specified volume, itis designed to turn off the first and the second switching means with the second voltage selected, and when the secondary battery voltage is judged to be lower than the second voltage with the second voltage selected, it is designed to turn on the secondswitching means and to supply the said constant current to the secondary battery for charging. According to this charging method, it is possible to achieve favorable charging by constant current.
The 36th invention is a charging equipment for charging the secondary battery which is charged by constant charging voltage, comprising a first voltage feeding means for feeding the first voltage to the secondary battery, a second voltage feedingmeans for feeding the second voltage lower than the first voltage to the secondary battery, a current detection means for detecting charging current to the secondary battery, and a control means for changing over the supply by the first voltage feedingmeans to and from the supply by the second voltage feeding means based on the detection results by the said current detection means, wherein when the current detecting means detects the first charging current corresponding to nearly full-charge by thecurrent detection means, the supply to the secondary battery is changed over from the first voltage feeding means to the second voltage feeding means, and at the same time, when the current detection means detects current exceeding the second chargingcurrent with the second voltage fed to the secondary battery from the second voltage feeding means by this change-over, the supply is changed over to that by the first voltage feeding means. According to this charging equipment, the battery is chargedto the full-charge condition by the first voltage only when the battery charging remainder lowers to a specified value. Consequently, once it is charged to the full-charge condition, charging to the full-charge is repeated every time the battery lowersto the specified battery charging remainder and the secondary battery is able to be constantly maintained to nearly full-charge condition, and at the same time, because the second voltage lower than the first voltage is applied to the battery except whencharging to this full-charge is carried out, the secondary battery is not brought to continuous full-charge condition, and deterioration of secondary battery performance caused by continued full-charge condition can be prevented.
The 37th invention is the charging equipment according to the 36th invention wherein the first charging current is the same as the second charging current. According to this charging equipment, the charging condition can be favorably controlled.
The 38th invention is the charging equipment according to the 36th invention, comprising the third voltage feeding means for feeding the third voltage of the potential across the first and the second voltages to the secondary battery, and atemperature detection means for detecting temperature inside or in the vicinity of the secondary battery, wherein only when the detected temperature of the secondary battery exceeds a predetermine temperature, the second voltage feeding means is changedover to the third voltage feeding means in place of changing over from the second voltage feeding means to the first voltage feeding means. According to this charging equipment, charging corresponding to temperature is favorably controlled.
The 39th invention is designed to continuously change the output voltage of the third voltage feeding means in accord with temperature detected by the temperature detection means in the charging equipment according to the 38th invention. According to this charging equipment, it is possible to finely control the charging voltage in accord with the then temperature at that time, and charging control corresponding to temperature can be favorably carried out.
The 40th invention is the charging equipment for charging the secondary battery in which charging is carried out by the constant voltage charging voltage, comprising a first voltage feeding means for feeding the first voltage to the secondarybattery, a second voltage feeding means for feeding the second voltage lower than the first voltage to the secondary battery, a current detection means for detecting the charging current to the secondary battery, a voltage detecting means for detectingone voltage of the secondary battery, and a control means for changing over the supply by the first voltage feeding means to and from the supply by the second voltage feeding means based on the detected result by the voltage detecting means, wherein whenthe specified voltage corresponding to the condition in which the secondary battery is nearly fully charged is detected by the voltage detection means, the supply to the secondary battery is changed over from the first voltage feeding means to the secondvoltage feeding means, and when the current detection means detects the current exceeding the predetermined charging current with the second voltage supplied from the second voltage feeding means to the secondary battery by this change-over, the supplyis changed over by the first voltage feeding means. According to this charging equipment, the battery is charged to the full-charge condition by the first voltage only when the battery charging remainder lowers to the specified value. Consequently,after the battery is charged to the full-charge condition once, charging to the full-charge is repeated every time the battery charging remainder lowers to a specified volume, and the secondary battery can constantly be maintained to a nearly chargedcondition, and at the same time, because the second voltage lower than the first voltage is applied to the battery except when charging to the full-charge is carried out, the secondary battery is not brought continuously to the full-charged condition,thereby preventing deterioration of the secondary battery performance caused by the continuation of the full-charged condition.
The 41st invention is the charging equipment according to the 40th invention, comprising the third voltage feeding means for feeding the third voltage of the potential across the first and the second voltage to the secondary battery and atemperature detection means for detecting the temperature inside or in the vicinity of the secondary battery, wherein when the detection temperature of the said temperature detecting means exceeds a specified temperature, the voltage feeding means ischanged over to the third voltage feeding means in place of changing over from the second voltage feeding means to the first voltage feeding means. According to this charging equipment, charging is able to be favorably controlled in accord with thetemperature.
The 42nd invention is the charging equipment according to the 41st invention, wherein the output voltage of the said third voltage feeding means is designed to be continuously changed in accord with the temperature detected by the saidtemperature detecting means. According to this charging equipment, it is possible to finely control the charging voltage in accord with the then temperature and to favorably control charging in accord with the temperature.
The 43rd invention is the charging equipment for charging the secondary battery requiring constant current charging at the start of charging, comprising a power supply circuit for feeding the specified charging power supply to the secondarybattery, a switching means connected across the said power supply circuit and the said secondary battery for controlling the start and stop of charging, a detecting means for detecting the potential across one end and the other end of the said switchingmeans or the potential across one end and the other end of the said secondary battery with the low-voltage charging power supply fed from the said power supply circuit, and a charging control means for starting charging to the secondary battery with thesaid switching means turned on based on the potential detected by the said detection means as well as the output voltage of the said power supply circuit set to a specified potential. According to this charging equipment, it is possible to detect thesecondary battery condition based on the control of the switching means and the detection of the potential across one end an the other end of the switching means or the potential across one end and the other end of the secondary battery, and toaccurately detect the condition of the secondary battery as in the case of the conventional pre-charging. Consequently, it is possible to precisely detect the secondary battery condition without providing a charging circuit special for pre-charging andsimplify the circuit configuration of the charging equipment.
The 44th invention is the charging equipment according to the 43rd invention, wherein a field-effect transistor is used for the said switching means, and the potential is designed to be detected by the said detection means by increasing theimpedance value across one end and the other end of the field-effect transistor. According to this charging equipment, the condition of the secondary battery can be easily detected only by controlling the impedance of the field-effect transistor, and atthe same time, even when the secondary battery voltage is low or shorted, it is possible to minimize the loss of the field-effect transistor, and to minimize the size of the transistor itself and a radiation plate, contributing to downsizing of thecharging equipment.
The 45th invention is the charging equipment according to the 43rd invention, wherein the output potential of the said power supply circuit when detected by the above detection means is set to the value in the vicinity of the lowest voltage atwhich the said charging control means operates. According to this charging equipment, it is possible to detect the secondary battery condition with the charging power supply of the lowest voltage fed to the secondary battery, to detect the electricalcondition of the secondary battery with the load to the secondary battery or circuit brought to the minimum, and to detect the electrical condition of the secondary battery under the favorable condition.
The 46th invention is the charging equipment according to the 43rd invention, wherein the output voltage of the said power supply is designed to increase with an increase of the potential across one end and the other end of the secondary voltageafter the start of charging. According to this charging equipment, the power applied to the switching means is able to be held nearly uniformly, and the condition of the switching means is able to be held favorably.
The 47th invention is the charging equipment according to the 43rd invention, wherein the output voltage of the said power supply circuit is designed to be varied in a plurality of stages with an increase of the potential across one end and theother end of the said secondary battery after the start of charging. According to this charging equipment, it is possible to keep the power supply applied to the switching means nearly uniformly and to keep the condition of the switching means in thefavorable condition. In this event, because the voltage is able to be varied in the plurality of stages, only simplified control is required for control of the voltage circuit.
The 48th invention is the charging equipment according to the 43rd invention, wherein a charged load storage means is connected across the said power supply circuit and the said charging control means, and to lower the output potential of thesaid power supply circuit when detected by the said detection means to the minimum voltage at which the charging control means lowers. According to this charging equipment, as long as electric charge is accumulated in the electric charge storage means,voltage of the charging power supply to be fed to the secondary battery in detecting by the detection means can be brought to the voltage lower than the voltage for controlling the switching means, and the condition of the secondary battery can bedetected more favorably with the still lower voltage applied.
The 49th invention is the charging equipment for charging the secondary battery to be charged by the constant voltage charging voltage, comprising a constant-voltage means for feeding the said charging voltage to the said secondary battery, abattery condition detecting means for detecting the said secondary battery condition, a charging control means for controlling charging by the constant-voltage means, and a timer means which operates when the said battery condition detecting meansdetects the specified condition of the said secondary battery, wherein a specified time passes from the start of operation of the timer means, the charging control means is designed to start charging by the said constant voltage means. According to thischarging equipment, it is possible to designate the time from the time when the battery once attains the full-charged condition (or nearly full-charged condition) to the time when charging is restarted as the time required for the battery to attain aspecified electrical condition with a specified time added, thereby securing some time before the battery returns to the full-charged condition even if an error occurs in the detection of the battery condition, and it is possible to prevent deteriorationof secondary battery characteristics caused by the continued full-charged condition.
The 50th invention is the charging equipment according to the 49th invention, wherein the said battery condition detection means is designed to detect the condition in which the secondary battery voltage attains a specified voltage. According tothis charging equipment, it is possible to accurately detect the lowering of battery voltage with the charging voltage set as a standard, enabling accurate control of the secondary battery condition.
The 51st invention is the charging equipment according to the 49th invention, wherein the said battery condition detection means is designed to detect the condition in which the charging current attains the specified value when the specifiedvoltage is applied to the above secondary battery. According to this charging equipment, it is possible to properly control the charging condition of the secondary battery based on the detection of the current value.
The 52nd invention is the charging equipment according to the 49th invention, wherein the constant voltage for pre-charging lower than the said charging voltage is designed to be fed as the said constant voltage means and this constant voltagefor pre-charging is designed to be used for the specified voltage applied to the said secondary battery. According to this charging equipment, it is possible to favorably set the voltage applied at the time of precharging.
The 53rd invention is the charging equipment for charging the secondary battery in which charging takes place by constant voltage charging voltage, comprising a constant voltage means for supplying the said charging voltage to the secondarybattery, a battery condition detection means for detecting the said secondary battery condition, a charging control means for controlling charging by the said constant voltage means, and a timer means for operating when the said battery conditiondetection means detects the nearly charged condition of the said secondary battery, wherein the said charging control means allows the said battery condition detection means to detect the condition of the said secondary battery every time nearly aspecified time passes from the time when the said timer means begins to operate, and when this detected condition falls in the specified condition, charging by the said constant voltage means is designed to be restarted. According to this chargingequipment, it is possible to keep at least a predetermined time open for the specified period from the time when charging is stopped once full-charge condition is attained to the time when charging is restarted, thereby enabling preventing ofdeterioration of the secondary battery characteristics.
The 54th invention is the charging equipment according to the 53rd invention, wherein charging by the constant voltage means is restarted after a specified time passes from the time when the specified condition is detected. According to thischarging equipment, it is possible to more effectively secure the time before it returns to the full-charge condition and to more improve the effect to prevent deterioration of the secondary battery characteristics.
The 55th invention is the charging equipment according to the 53rd invention, wherein the said battery condition detection means is designed to detect as the specified condition detection that the charging current exceeds a specified value whenthe said charging voltage or voltage lower than this charging voltage is applied to the said secondary battery. According to this charging equipment, it is possible to accurately detect the secondary battery condition from the charging current.
The 56th invention is the charging equipment according to the 53rd invention, wherein the said battery condition detection means is designed to detect as the specified condition detection that the battery voltage of the said secondary batteryattains the specified voltage. According to this charging equipment, it is possible to accurately detect the secondary battery condition from the battery voltage.
The 57th invention is the charging equipment according to the 56th invention, wherein at least the energy required for detecting the battery voltage in the said secondary battery is designed to be charged in the secondary battery by the controlof the said charging control means when the said secondary battery voltage does not attain the specified voltage and charging is not restarted. According to this charging equipment, it is possible to effectively prevent the decrease of remaining voltagecaused by repeating detection of the battery condition every specified time.
The 58th invention is the charging equipment for charging the secondary battery, comprising a first voltage supply means for supplying the first voltage to the secondary battery, a second voltage supply means for supplying the second voltagelower than the said first voltage to the secondary battery, a selection means for changing over the charging voltage applied to the said secondary battery between the said first and second voltage supply means, a switching means for ON-OFF controllingthe application of the output voltage of the first or second voltage supply means selected by the selection means to the secondary battery, a detecting means for detecting the electrical condition of the said secondary battery, and a control means forcontrolling the selection with the said selection means and ON/OFF control by the said change-over means in accord with the condition detected by the detection means. According to this charging equipment, it is possible to select the first and thesecond voltages for the voltage applied to the secondary battery, and at the same time, to be able to carry out ON-OFF control of the application of this selected voltage, to prevent discharge from the battery to the charging circuit side when chargingvoltage lower than the battery voltage is established, thereby preventing wasteful discharge of the secondary battery when voltage applied to the secondary battery is allowed to be varied.
The 59th invention is the charging equipment according to the 58th invention, wherein when the said control means judges that the charged volume of the secondary battery is lower than the specified volume, the said switching means is turned onand at the same time the first voltage supply means is selected by the selection means to apply the first voltage to the secondary battery for charging, and when the said control means judges that the secondary battery is charged to the specified volume,the said switching means is turned off, and at the same time the second voltage feeding means is selected by the said selection means, and when the said control means judges that the secondary battery voltage is lower than the second voltage under thestate that the second voltage feeding means is selected, the switching means is turned on by control of the said control means to apply the second voltage to the secondary battery for charging. According to this charging equipment, it is possible toeffectively prevent wasteful discharge from the secondary battery and at the same time to be able to charge the second voltage to the secondary battery free of detrimental effects when charging is restarted.
The 60th invention is the charging equipment according to the 59th invention, wherein for the said control means to judge that the secondary battery voltage is lower than the second voltage is when it is judged that the voltage is lower than thesecond voltage again in a specified time after it is judged at least once that the voltage is lower than the second voltage. According to this charging equipment, it is possible to charge the secondary battery with the second voltage when the secondarybattery voltage is positively lower than the second voltage and to restart charging under the favorable condition free of deteriorating the secondary battery.
The 61st invention is the charging equipment according to the 59th invention, wherein it is when the secondary battery voltage is the third voltage lower than the second voltage that the second voltage feeding means applies the said secondvoltage to the secondary battery for charging. According to this charging equipment, it is possible to restart charging under the favorable condition free of deteriorating the secondary battery only by judgment of the battery voltage without countingpassage of time.
The 62nd invention is the charging equipment according to the 59th invention, wherein the potential difference between one end and the other end of the switching means is detected for judging that the said secondary battery voltage is lower thanthe second voltage. According to this charging equipment, it is possible to accurately judge the battery voltage at the restart of charging.
The 63rd invention is the charging equipment according to the 59th invention, wherein it is judged whether or not the said secondary battery voltage is lower than the said second voltage when the current of the said secondary battery is judged tobe lower than the specified current value when the said switching means is turned off. According to this charging equipment, charging processing at the second voltage is carried out only when the current flowing in the load circuit is lower than thespecified value (for example, in the case of the vicinity of zero), and it is possible to prevent charging at a low voltage when the load current exceeds the specified value.
The 64th invention is the charging equipment according to the 59th invention, wherein the potential difference between one end and the other end of the switching means is detected when the said secondary battery current is judged lower than thespecified current when the said switching means is turned off and it is judged that the said secondary battery voltage is lower than the said second voltage. According to this charging equipment, it is possible to judge the restart of charging byaccurate voltage judgment based on the potential difference between one end and the other end of the switching means only when the current flowing in the load current is lower than the specified value.
The 65th invention is the charging equipment according to the 58th invention, wherein when the said control means judges that the charged volume of the secondary battery is lower than the specified volume, the switching means is turned on and atthe same time, the first voltage feeding means is selected with the said selecting means to apply and charge the first voltage to the secondary battery, and when the control means judges that the charged volume of the secondary battery is charged to thespecified volume, the switching means is turned off, and at the same time the second voltage feeding means is selected by the said selecting means, and the second voltage is applied to the secondary battery to change the same with the switching meansturned on by the control of the control means when the current flowing in the secondary battery is judged again to be lower than the specified value at least in the specified time after the control means judges that the current flowing in the secondarybattery is lower than the specified value with this second voltage feeding means selected. According to this charging equipment, it is possible to effectively prevent wasteful discharge from the secondary battery as well as to judge the restart ofcharging based on judgment of the current.
The 66th invention is the charging equipment according to the 65th invention, wherein the current flowing in the current path connected to the said secondary battery different from the current path fed to the said secondary battery via theswitching means is detected for the current flowing to the said secondary battery. According to this charging equipment, it is possible to detect the stable current value not subject to fluctuation of voltage applied.
The 67th invention is the charging equipment according to the 58th invention, wherein the first and the second switching means are provided in parallel as the said switching means and a constant current output means is connected to the secondswitching means, and when the charged volume of the secondary battery is judged to be lower than the specified volume, the first switching means is turned on and the second switching means is turned off, and at the same time the first voltage feedingmeans is selected by the selecting means to apply and charge the first voltage to the secondary battery, and when the control means judges that the charged volume of the secondary battery is charged to the specified volume, the first and the secondswitching means are turned off and the second voltage feeding means is selected with the selecting means, and when the control means judges that the second battery voltage is lower than the second voltage with this second voltage feeding means selected,the control means controls to turn on the second switching means and to turn off the first switching means, and the output of the constant current output means is supplied to charge the secondary battery. According to this charging equipment, it ispossible to achieve favorable charging by constant current.
The 68th invention is an integrated circuit for controlling charging of the secondary battery in which control is carried out for selectively supplying the first voltage and the second voltage lower than this first voltage to the said secondarybattery, and when the secondary battery is judged to be nearly fully charged based on the judgment of the detected charging current while control is being carried out for applying and charging the first voltage to the secondary battery, control iscarried out for changing over to the application of the second voltage to the secondary battery, and when the secondary battery is judged to have a specified battery remaining voltage based on the judgment of the detected charging current while controlof applying this second voltage is being underway, control is carried out for changing over to the application of the first voltage to the secondary battery. According to this integrated circuit, control for charging to the full-charge condition by thefirst voltage is carried out only when the remaining battery volume lowers to the specified volume. Consequently, after the battery is charged to the full-charge condition once, charging to the full-charge is repeatedly carried out every time thebattery lowers to the specified battery charging remainder, thereby maintaining the secondary battery condition constantly to the nearly full-charge condition, and at the same time, because except when charging to this full-charging is carried out, thesecond voltage lower than the first voltage is applied to the battery, the secondary battery does not reach the full-charge condition continuously, enabling favorable charging control in which deterioration of the secondary battery performance caused bycontinued full-charge condition can be prevented.
The 69th invention is an integrated circuit according to the 68th invention, wherein when the temperature is higher than a specified temperature based on the judgment of the detected temperature inside or in the vicinity of the secondary battery,control is carried out for applying the third voltage across the first voltage and the second voltage to the secondary battery. According to this integrated circuit, it is possible to favorably carry out charging control while suppressing thedeterioration of performance of the secondary battery due to temperature rise of the battery.
The 70th invention is an integrated circuit according to the 69th invention, wherein the third voltage is controlled to be continuously varied based on the judged temperature. According to this integrated circuit, the charging voltage can befinely controlled in accord with the temperature at the time and charging can be more favorably carried out in accord with temperature.
The 71st invention is an integrated circuit for controlling charging of the secondary battery in which control is carried out for selectively supplying the first voltage or the second voltage lower than this first voltage to the said secondarybattery, and when the secondary battery is judged to be nearly fully charged based on the judgment of the detected charging voltage while control is being carried out for applying and charging the first voltage to the secondary battery, control iscarried out for changing over to the application of the second voltage to the secondary battery, and when the secondary battery is judged to have a specified battery remaining voltage based on the judgment of the detected charging voltage while controlof applying this second voltage is being underway, control is carried out for changing over to the application of the first voltage to the secondary battery. According to this integrated circuit, control for charging to the full-charge condition by thefirst voltage is carried out only when the remaining battery volume lowers to the specified volume. Consequently, after the battery is charged to the full-charge condition once, charging to the full-charge is repeatedly carried out every time thebattery lowers to the specified battery charging remainder, thereby maintaining the secondary battery condition constantly to the nearly full-charge condition, and at the same time, because except when charging to this full-charging is carried out, thesecond voltage lower than the first voltage is applied to the battery, the secondary battery does not reach the full-charge condition continuously, enabling favorable charging control in which deterioration of the secondary battery performance caused bycontinued full-charge condition can be prevented.
The 72nd invention is an integrated circuit according to the 71st invention, wherein when the temperature is higher than the specified temperature based on the judgment of the detected temperature inside or in the vicinity of the secondarybattery, control is carried out for applying the third voltage across the first voltage and the second voltage to the secondary battery. According to this integrated circuit, it is possible to favorably carry out charging control while suppressing thedeterioration of performance of the secondary battery due to temperature rise of the battery.
The 73rd invention is an integrated circuit according to the 69th invention, wherein the third voltage is controlled to be continuously varied based on the judged temperature. According to this integrated circuit, the charging voltage can befinely controlled in accord with the temperature at the time and control of charging can be more favorably carried out in accord with temperature.
The 74th invention is an integrated circuit for controlling charging of the secondary battery, wherein the detected value of the potential across one end and the other end of the switching means for controlling start and stop of the supply of thecharging power supply to the secondary battery or the potential across one end and the other end of the secondary battery is judged while control for supplying the low-voltage charging power supply to the secondary battery is being carried out, and whenthis judged potential is a specified potential, control for turning on the switching means is carried out and at the same time control for setting the charging power supply supplied to the secondary battery to the specified potential is carried out sothat control for starting the charging to the secondary battery takes place. According to this integrated circuit, it is possible to control the switching means and to detect the secondary battery condition based on the detection of the potential acrossone end and the other end of this switching means or the potential across one end and the other end of the secondary battery, thereby enabling accurate detection of the secondary battery condition as in the case of conventional pre-charging. Consequently, it is possible to precisely detect the secondary battery without providing a charging circuit specialized for pre-charging, and it is possible to simplify the circuit configuration of the charging equipment.
The 75th invention is an integrated circuit according to the 74th invention, wherein the detected value of the potential across one end and the other end of the secondary battery after the said charging begins is judged, and control is carriedout to raise the potential of the charging power supply in accordance with the increase of the judged potential. According to this integrated circuit, it is possible to hold the power supply applied to the switching means nearly uniformly, therebyenabling the control for maintaining the switching means to a favorable condition.
The 76th invention is an integrated circuit according to the 74 invention, wherein the detected value of the potential across one end and the other end of the secondary battery after the charging begins is judged, and control for raising thepotential of the charging power supply by varying it in a plurality of stages in accord with an increase of the judged potential. According to this integrated circuit, it is possible to nearly uniformly keep the electric power applied to the switchingmeans, and it is also possible to keep the switching means to the favorable condition. In this case, since voltage is allowed to be varied in a plurality of stages, a simple control is only required for control of the voltage circuit.
The 77th invention is an integrated circuit for controlling the charging of the secondary battery, wherein if it is judged that the battery reaches a specified electrical condition based on the specified electrical detection data related to thesecondary battery after carrying out the control for stopping the charging operation when charging operation by constant voltage is carried out and it is judged that the secondary battery reached the nearly full-charged condition, control is carried outto restart the charging operation of the secondary battery after a specified time passes from this judgment of this specified electrical condition. According to this integrated circuit, it is possible to designate the time to restart charging once itcomes in the full-charge state (or nearly full-charge state) to the time in which a specified time is added to the time for a battery to reach a specified electrical condition, and even if any error exists in the detected battery condition, it ispossible to secure a certain time for returning to the full-charge condition, and it is thereby possible to carry out favorable control to prevent deterioration of characteristics of the secondary battery caused by continuation of the full-chargeconditions.
The 78th invention is an integrated circuit according to the 77th invention, wherein the said specified electrical condition is judged by judging that the battery voltage of the said secondary battery reaches the specified voltage. According tothis integrated circuit, it is possible to exactly judge the condition of the secondary battery by the judgment of the battery voltage.
The 79th invention is an integrated circuit according to the 77th invention, wherein the said specified electrical condition is judged by judging that the charging current reaches a specified current value when a specified voltage is applied tothe secondary battery. According to this integrated circuit, it is possible to exactly judge the secondary battery condition by judgment of the charging current.
The 80th invention is an integrated circuit according to the 79th invention, wherein control is made to apply the said specified voltage to the secondary battery, which is lower than the charging voltage of the said constant voltage. Accordingto this integrated circuit, it is possible to detect the secondary battery condition by the voltage lower than the charging voltage, and to properly detect the battery condition with a load applied to the secondary battery reduced.
The 81st invention is an integrated circuit for controlling the charging of the secondary battery in which charging is carried out by constant voltage charging to judge that the secondary battery reaches the nearly
full-charged condition, and after control for stopping the charging operation is carried out, the specified electrical detection data related to the secondary battery is judged every time a specified time passes from the stopping of thischarging operation, and when it is judged that the battery enters a specified electrical condition by this judgment, control is carried out for restarting the charging operation. According to this integrated circuit, it is possible to keep the time openat least for the specified period from the time when charging is stopped once full-charge condition is attained to the time when charging is restarted, thereby enabling control while preventing the deterioration of the secondary battery characteristics.
The 82nd invention is an integrated circuit according to the 81st invention, wherein control is carried out to restart charging after a specified time passes from the time when the specified electrical condition is judged. According to thisintegrated circuit, it is possible to more effectively secure the time before it returns to the full-charge condition and to more improve the effect to prevent deterioration of the secondary battery characteristics.
The 83rd invention is an integrated circuit according to the 81st invention, wherein the specified electrical condition is judged by judging that the detected charging current exceeds a specified value while control for applying a constantvoltage or specified voltage lower than this constant voltage is being applied to the said secondary battery. According to this integrated circuit, it is possible to accurately detect the secondary battery condition from judgment of the chargingcurrent.
The 84th invention is an integrated circuit according to the 81st invention, wherein the specified electrical condition is judged by judging that the detected secondary battery voltage reaches a specified voltage. According to this integratedcircuit, it is possible to accurately detect the secondary battery condition from judgment of the charging current.
The 85th invention is an integrated circuit according to the 84th invention, wherein control is carried out so that at least the energy required for detecting the battery voltage in the said secondary battery is designed to be charged to thesecondary battery when it is judged that the detected value of the secondary battery voltage does not attain the specified voltage and charging is not restarted. According to this integrated circuit, it is possible to carry out control for effectivelypreventing the decrease of remaining voltage caused by repeating detection of the battery condition every specified time.
The 86th invention is an integrated circuit for controlling the charging of the secondary battery, wherein control is carried out for selectively supplying the first voltage and the second voltage lower than the said first voltage to thesecondary battery, and detected value of the electrical condition of the secondary battery is judged, and in accord with the judged detected value, the first voltage and the second voltage are selected for the voltage to be applied to the secondarybattery, and ON-OFF control is carried out for applying the selected voltage to the secondary battery. According to this integrated circuit, it is possible to select the first and the second voltages for the voltage applied to the secondary battery, andat the same time, to be able to carry out ON-OFF control of the application of this selected voltage, to prevent discharge from the battery to the charging circuit side when charging voltage lower than the battery voltage is established, and to enablethe control for preventing wasteful discharge of the secondary battery when voltage applied to the secondary battery is allowed to be varied.
The 87th invention is an integrated circuit according to the 86th invention, wherein when based on the judgment of the detection value of the electrical condition of the said secondary battery, it is judged that the secondary battery is chargedto the specified volume, the second voltage is selected and at the same time control for turning off the application of this voltage to the secondary battery, and if it is judged that under this condition, the secondary battery voltage reaches below thesecond voltage, control for turning on the application of the second voltage to the secondary battery is carried out. According to this integrated circuit, it is possible to effectively prevent wasteful discharge from the secondary battery and at thesame time to be able to control of the charging of the second voltage to the secondary battery free of detrimental effects when charging is restarted.
The 88th invention is an integrated circuit according to the 87th invention, wherein to judge that the secondary battery voltage is lower than the second voltage is when it is judged that the voltage is lower than the second voltage again in aspecified time after it is judged at least once that the voltage is lower than the second voltage. According to this integrated circuit, it is possible to charge the secondary battery with the second voltage when the secondary battery voltage ispositively lower than the second voltage and to restart charging under the favorable condition free of deteriorating the secondary battery.
The 89th invention is an integrated circuit according to the 87th invention, wherein it is when it is judged that the secondary battery voltage is the third voltage lower than the second voltage that the said second voltage is applied and chargedto the secondary battery. According to this integrated circuit, it is possible to restart charging under the favorable condition free of deteriorating the secondary battery only by judgment of the battery voltage without counting passage of time.
The 90th invention is an integrated circuit according to the 87th invention, wherein it is judged that the said secondary battery voltage is lower than the said second voltage when the current of the said secondary battery is judged to be lowerthan the specified current value when voltage application to the said secondary battery is turned off. According to this integrated circuit, charging processing at the second voltage is carried out only when the current flowing in the load circuit islower than the specified value (for example, in the case of the vicinity of zero), and it is possible to prevent charging at a low voltage when the load current exceeds the specified value.
The 91st invention is an integrated circuit according to the 87th invention, wherein when the secondary battery current is judged to be lower than the specified value when application of the voltage to the secondary battery is turned off, thepotential difference between one end and the other end of the switching means for carrying out the ON/OFF control is detected and the secondary battery voltage is judged to be lower than the second voltage. According to this integrated circuit, it ispossible to judge the restart of charging by accurate voltage judgment based on the potential difference between one end and the other end of the switching means only when the current flowing in the load current is lower than the specified value.
The 92nd invention is an integrated circuit according to the 86th invention, wherein when it is judged that the charged volume of the secondary battery is lower than the specified volume, control is carried out for turning on the application ofthe voltage to the secondary battery to charge the same with the first voltage selected, and when it is judged that the secondary battery is charged to the specified volume, control is carried out for turning off the application of the voltage to thesecondary battery with the second voltage selected, and when it is judged that the current flowing in the secondary battery again at least after a specified time after it is judged that the current flowing in the secondary battery is lower than thespecified value with this second voltage selected, control is carried out for selecting the second voltage and turning on the application of the voltage to the secondary voltage for charging. According to this integrated circuit, it is possible toeffectively prevent wasteful discharge from the secondary battery as well as to judge the restart of charging based on judgment of the current.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is an explanatory diagram showing one example of charging characteristics of a lithium ion battery.
FIG. 2 is a structural diagram showing one example of a conventional charging equipment.
FIG. 3 is a characteristic diagram showing charging characteristics of the example of FIG. 2.
FIG. 4 is a structural diagram showing another example of the conventional charging equipment.
FIG. 5 is a characteristic diagram showing charging characteristics of the example of FIG. 4.
FIG. 6 is a characteristic diagram showing one example of the recharging condition of the conventional lithium battery.
FIG. 7 is a structural diagram showing a charging equipment according to the first embodiment of this invention.
FIG. 8 is a flow chart showing charging processing according to the first embodiment.
FIG. 9 is a characteristic diagram showing the charging condition according to the first embodiment.
FIG. 10 is a flow chart showing charging processing when full-charge detection is carried out by another processing in the first embodiment.
FIG. 11 is a flow chart showing charging processing when full-charge detection is carried out by still another processing in the first embodiment.
FIG. 12 is a flow chart showing charging processing when full-charge detection is carried out by still further processing in the first embodiment.
FIG. 13 is a flow chart when control of charging processing at the time of full-charge of the first embodiment is carried out by temperature.
FIG. 14 is a structural diagram showing a charging equipment according to the second embodiment of this invention.
FIG. 15 is a flow chart showing charging processing according to the second embodiment.
FIG. 16 is a characteristic diagram showing the charging condition according to the second embodiment.
FIG. 17 is a flow chart showing the charging processing when voltage is varied in the three stages by temperature in the second embodiment.
FIG. 18 is a structural diagram showing a charging equipment according to the third embodiment of this invention.
FIG. 19 is a flow chart showing charging processing according to the third embodiment.
FIG. 20 is a structural diagram showing a charging equipment according to the fourth embodiment of this invention.
FIG. 21 is a flow chart showing charging processing according to the fourth embodiment.
FIG. 22 is a flow chart showing charging processing according to the fifth embodiment of this invention.
FIG. 23 is a structural diagram showing a charging equipment according to the sixth embodiment of this invention.
FIG. 24 is a flow chart showing charging processing according to the sixth embodiment.
FIG. 25 is a characteristic diagram showing the charging condition according to the sixth embodiment.
FIG. 26 is a structural diagram showing a charging equipment according to the seventh embodiment of this invention.
FIG. 27 is a characteristic diagram showing the charging condition according to the seventh embodiment.
FIG. 28 is a structural diagram showing a charging equipment according to the eighth embodiment of this invention.
FIG. 29 is a structural diagram showing a charging equipment applied to the ninth embodiment of this invention.
FIG. 30 is a flow chart showing charging processing according to the ninth embodiment.
FIG. 31 is a characteristic diagram showing the charging condition according to the ninth embodiment.
FIG. 32 is a flow chart showing charging processing when full-charge detection is carried out by another processing in the ninth embodiment.
FIG. 33 is a characteristic diagram showing the charging condition according to the example of FIG. 32.
FIG. 34 is a flow chart showing charging processing according to the tenth embodiment of this invention.
FIG. 35 is a characteristic diagram showing the charging condition according to the tenth embodiment.
FIG. 36 is a flow chart showing charging processing when full-charge detection is carried out by another processing in the tenth embodiment.
FIG. 37 is a flow chart showing charging processing when full-charge detection is carried out by still another processing in the tenth embodiment.
FIG. 38 is a characteristic diagram showing the charging condition according to the 11th embodiment of this invention.
FIG. 39 is a structural diagram showing a charging equipment according to the 12th embodiment of this invention.
FIG. 40 is a flow chart showing charging processing by the 12th embodiment.
FIG. 41 is a flow chart showing charging condition by the modified example of the 12th embodiment.
FIG. 42 is a structural diagram showing a charging equipment according to the 13th embodiment of this invention.
FIG. 43 is a flow chart showing charging processing by the 13th embodiment.
FIG. 44 is a structural diagram showing a charging equipment according to the 14th embodiment of this invention.
FIG. 45 is a flow chart showing charging processing by the 14th embodiment.
FIG. 46 is a structural diagram showing a charging equipment according to the 15th embodiment of this invention.
FIG. 47 is a flow chart showing charging processing by the 15th embodiment.
FIG. 48 is a structural diagram showing a charging equipment according to the 16th embodiment of this invention.
FIG. 49 is a flow chart showing charging processing by the 16th embodiment.
FIG. 50 is a structural diagram showing a charging equipment according to the 17th embodiment of this invention.
FIG. 51 is a structural diagram showing a charging equipment according to the 18th embodiment of this invention.
FIG. 52 is a flow chart showing charging processing by the 18th embodiment.
BEST MODE FOR CARRYING OUT THE INVENTION
Now, the first embodiment of this invention will be described with reference to FIG. 7-FIG. 13.
FIG. 7 is a block diagram showing the configuration of the charging equipment of this embodiment, where AC power supply (about 100V-240V) from a commercial AC power supply 11 is supplied to a transformer/rectifier circuit 12 to provide a DClow-voltage power supply. This DC low-voltage power supply is supplied to a constant current circuit 13 to produce an output of constant current. And this constant-current output is supplied to a movable contact 14m of a change-over switch 14. Firstand second fixed contacts 14a and 14b of this change-over switch 14 are connected to constant voltage circuits 15 and 16, respectively, and a specified voltage is outputted from the constant voltage circuit 15 or 16 on the side to which the movablecontact 14m is connected. In this event, the constant voltage circuit 15 is designed to output 4.2V, while the constant voltage circuit 16 is designed to output 4.0V.
To the positive electrode side of a secondary battery 17 loaded on this charging equipment, the output voltage of the constant voltage circuit 15 or 16 is applied. In this event, in this example, a lithium ion battery is used for the secondarybattery 17. The lithium ion battery used here must provide characteristics in which the battery voltage is 4.2V when the battery is 100% charged (fully charged).
Then, the potential difference between the positive electrode side and the negative electrode side of this secondary battery 17 is detected with a voltage detection circuit 18. The data of voltage values detected by this voltage detectioncircuit 18 is supplied to a control circuit 21 later
described.
The negative electrode side of the secondary battery 17 is connected to the transformer/rectifier circuit 12 via a current detection resistor 19 to form a charging circuit of the secondary battery 17. Based on the potential difference betweenone end and the other end of the current detection resistor 19, the current flowing through the resistor 19 is detected by a current detection circuit 20. The current value detected by this current detection circuit 20 corresponds to the chargingcurrent supplied to the secondary battery 17. The data of current values detected by the current detection circuit 20 is supplied to the control circuit 21. This control circuit 21 is a circuit composed by a microcomputer with integrated circuits forcontrolling the charging operation, and based on the comparison between the data of current values detected by the current detection circuit 20 and a current value I.sub.1 stored in advance in the control circuit 21, the connection condition of themovable contact 14m of the change-over switch 14 is controlled. In this event, for this current value I.sub.1, the charging current value when the secondary battery 17 is 100% charged with the charging voltage 4.2V is used.
By the way, there is a case in which a load circuit 28 may be connected to the secondary battery 17.
Now, referring to the flow chart of FIG. 8, processing when the secondary battery (lithium ion battery) is charged with this charging equipment will be described.
First of all, the control circuit 21 detects whether there is the secondary battery 17 or not (that is, whether it is loaded on the charging equipment or not) (Step S101). The presence of the battery 17 is judged by electrical detection, such asdetection of the battery voltage and so on or mechanical detection, and either detection is acceptable.
Based on the detection results, whether the battery is present or not is judged (Step S102), and if it is judged that the battery is present, the movable contact 14m of the change-over switch 14 is connected to the fixed contact 14a, and with the4.2-V charging voltage V.sub.1 outputted by the first constant voltage circuit 15, charging of the battery 17 is carried out (Step S103). And in this event, charging current is detected by the current detection circuit 20 (Step S104), and judgment ismade on whether the detected charging current value is lower than the specified value I.sub.1 previously set or not (Step S105).
In this event, if the current exceeds the setting value I.sub.1, the flow returns to Step S103 and charging with 4.2V charging voltage V.sub.1 is continuously carried out. When it is judged that the current is lower than the setting valueI.sub.1 at Step S105, processing for stopping charging is carried out (Step S106), the movable contact 14m of the changeover switch 14 is changed over to the second fixed contact 14b from the first fixed contact 14a, and the 4.0-V charging voltageV.sub.2 outputted from the second constant voltage circuit 16 is applied to the secondary battery 17 (Step S107).
Under th is condition, charging current is detected by the current detection circuit 20 (Step S108), the detected charging current value I.sub.2 is compared with the previously set specified value I.sub.1 (Step S109), and if the charging currentvalue I.sub.2 is lower than the setting value I.sub.1, the flow returns to Step S108, and current detection is continuously carried out. If in this current detection, the current value I.sub.2 exceeds the setting value I.sub.1 (that is, I.sub.2.gtoreq.I.sub.1), the movable contact 14m of the changeover switch 14 is changed over to the first fixed contact 14a from the second fixed contact 14b, the 4.2-V charging voltage V.sub.1 outputted by the first constant voltage circuit 15 is applied tothe secondary battery 17, and charging is allowed to take place with this 4.2V charging voltage V.sub.1 (Step S110). Then, the flow returns to Step S104, and the charging current is detected by the current detection circuit 20.
A shown in the flow char t of FIG. 8, controlling the charging operation with the control circuit 21 allows charging to take place with the characteristics shown in FIG. 9. FIG. 9 is a characteristic diagram in which charging current/voltage isplotted against the elapsed time, and constant current charging with the charging current I set as a constant current is carried out from the start of charging until the battery voltage attains a specified potential (in this example, the arrangement tocarry out constant current charging is omitted), and then, charging is changed over to constant-voltage charging, and charging takes place with the 4.2V charging voltage V.sub.1. The execution of this constant voltage charging causes the battery voltageV to coincide with the charging voltage V.sub.1, but the charging current I gradually decreases, and the charging current I becomes the value lower than the previously set current value I.sub.1. The charging current reaching the value lower than thiscurrent value I.sub.1 means that the secondary battery (lithium ion battery) is 100% charged.
At the timing when the secondary battery is 100% charged, that is, at the timing T.sub.1 when the charging current becomes lower than the current value I.sub.1, the changeover s | | | |
